In a the mold opening and locking mechanism in an injection molding machine or the like there is provided a pair of molds consisting of a fixed mold and a movable mold. The former is supported by a fixed plate and the latter is supported by a movable plate. When molding is effected during locking of the mold, the movable mold must be locked firmly to the fixed mold so as to be prevented from moving away from the fixed mold. The disadvantage in conventional mold opening and locking mechanisms is that, when producing larger-sized molded articles, a mold opening and locking mechanism of larger size is required. As a result, a hydraulic means and a toggle means are by necessity required to be designed larger in size. The present invention seeks to eliminating the aforegoing disadvantage.